1. Field of the Invention
This invention lies in the field of the flaring of waste gases by burning at the top of the flare stack in such a manner as to provide smokeless combustion, with minimum pollutants going into the atmosphere.
This invention further lies in the use of hot water to provide a mixture of water vapor with the flowing waste gases, upstream of the burning point at the top of the flare.
2. Description of the Prior Art
It is well known in smokeless combustion of hydrocarbon gases, if there is mixed with the flowing gases a sufficiently high mol percent of water vapor, that in the heat of the burning zone there will be a chemical reaction which converts methane and water into carbon monoxide and hydrogen, the burning of which provide smokeless combustion. If there is sufficient mixture of water vapor, and if the flame is hot enough to carry out the chemical reactions, there will be smokeless combustion.
This chemical reaction requires that the water be in the vapor phase, and also be of adequate mol percentage, or partial pressure of water vapor, to permit the water vapor-hydrogen chemistry to occur to a great enough degree. The function of water vapor mol percentage in gases is according to the saturation temperature, and the amount of water vapor as contained by gases as a function of temperature is as follows:
60.degree. F. -- 1.75% PA1 70.degree. f. -- 2.75% PA1 80.degree. f. -- 3.60% PA1 90.degree. f. -- 4.90% PA1 100.degree. f. -- 6.45% PA1 120.degree. f. -- 11.50%
The water vapor contents as shown, are for a condition of saturation at each temperature. In each case, if the temperature should fall the contained water vapor will reach its dew-point, and condense as liquid water, and the residual water vapor would be that for the lower temperature.
This process, in which the chemistry indicated above provides useful smoke reduction, is brought about by the water vapor mixed with the hydrocarbon gases. Therefore, the temperature of the gas-water vapor mixture is a key to accomplishment of the desired chemical reaction. Further, this reaction requires the supply of heat from combustion, of approximately 90,000 btu/mol. This is supplied by the flame itself. However, in the practice of smoke suppression, a full molar reaction is not required. Most hydrocarbons in burning in the atmosphere show marked smoke reduction, when as little as 3% water vapor is contained in the hydrocarbon, as it begins to burn. Of course, higher water vapor mol percent is preferable. This is true because flare vented hydrocarbons are normally "bone dry", such that water vapor content is typically measured in parts per million.
From the water vapor-mol percent data as shown above, it is evident that the effect of water vapor in flare vented gases begins to occur when the gas water vapor mixture discharged for burning is as warm as is possible. Since gases enroute to the flare are frequently at lower temperature, some means for heat supply to the mixture must be provided.